路漫漫其修遠兮，吾將上下而求索
經驗淺薄，耐心積累；記性不好，記諸文字

隨筆-204 評論-149 文章-0 trackbacks-0

前一個是直接生成了一個一個方法對原方法進行調用，現在直接在原方法上進行修改
即將

public class StringBuilder

{

private String buildString(int length) {

String result = "";

for (int i = 0; i < length; i++) {

result += (char)(i%26 + 'a');

}

System.out.println(result);

return result;

}

public static void main(String[] argv) {

StringBuilder inst = new StringBuilder();

for (int i = 0; i < argv.length; i++) {

String result = inst.buildString(Integer.parseInt(argv[i]));

System.out.println("Constructed string of length " +

result.length());

}

改成：

public class StringBuilder

{

private String buildString(int length) {

System.out.println("start start start");
long starttime = System.currentTimeMillis();

String result = "";

for (int i = 0; i < length; i++) {

result += (char)(i%26 + 'a');

}

System.out.println(result);

        System.out.println("Call to buildString$impl took " +
                (System.currentTimeMillis()-starttime) + " ms.");
        System.out.println("end end end end");

return result;

}

public static void main(String[] argv) {

StringBuilder inst = new StringBuilder();

for (int i = 0; i < argv.length; i++) {

String result = inst.buildString(Integer.parseInt(argv[i]));

System.out.println("Constructed string of length " +

result.length());

}

修改代碼如下：

import java.io.FileOutputStream;

import java.util.Iterator;

import org.apache.bcel.Constants;

import org.apache.bcel.classfile.ClassParser;

import org.apache.bcel.classfile.JavaClass;

import org.apache.bcel.classfile.LineNumberTable;

import org.apache.bcel.classfile.LocalVariableTable;

import org.apache.bcel.classfile.Method;

import org.apache.bcel.generic.ClassGen;

import org.apache.bcel.generic.ConstantPoolGen;

import org.apache.bcel.generic.InstructionConstants;

import org.apache.bcel.generic.InstructionFactory;

import org.apache.bcel.generic.InstructionHandle;

import org.apache.bcel.generic.InstructionList;

import org.apache.bcel.generic.InvokeInstruction;

import org.apache.bcel.generic.LocalVariableGen;

import org.apache.bcel.generic.MethodGen;

import org.apache.bcel.generic.ObjectType;

import org.apache.bcel.generic.PUSH;

import org.apache.bcel.generic.Type;

public class BCELTiming2 {

private static void modifyWrapper(ClassGen cgen,Method method){

InstructionFactory ifact = new InstructionFactory(cgen);

ConstantPoolGen pgen = cgen.getConstantPool();

String cname = cgen.getClassName();

MethodGen wrapgen = new MethodGen(method,cname,pgen);

//除掉這個原來的方法

cgen.removeMethod(method);

System.out.println("打印出這個方法看看---------------------------------start");

System.out.println(wrapgen.toString());

System.out.println("打印出這個方法看看---------------------------------end");

InstructionList ilist = wrapgen.getInstructionList();

System.out.println("看看這個方法的InstructionList-----------------------------start");

System.out.println(ilist.toString());

System.out.println("看看這個方法的InstructionList-----------------------------start");

System.out.println("看看這個方法InstructionList的各個InstructionHandle的信息--------------------start");

Iterator handleIt = ilist.iterator();

while(handleIt.hasNext()){

InstructionHandle iHandle = (InstructionHandle)handleIt.next();

System.out.println(iHandle.getAttributes());

System.out.println(iHandle.toString());

}

System.out.println("看看這個方法InstructionList的各個InstructionHandle的信息--------------------end");

System.out.println("先看看此方法的LocalVariableTable的信息--------------------------------------start");

LocalVariableTable lvt = wrapgen.getLocalVariableTable(pgen);

System.out.println(lvt.toString());

System.out.println("先看看此方法的LocalVariableTable的信息--------------------------------------end");

LineNumberTable lnt = wrapgen.getLineNumberTable(pgen);

System.out.println("LineNumberTable--------------------------------------start");

System.out.println(lnt.toString());

System.out.println("LineNumberTable--------------------------------------end");

Type returnType = wrapgen.getReturnType();

Type[] types = wrapgen.getArgumentTypes();

int slot = wrapgen.isStatic()?0:1;//非靜態方法slot 0處應該存儲的是this

//// 這種方式與Java如何處理方法調用有關。對于非靜態的方法，每次調用的第一個（隱藏的）參數是目標對象的this引用（就是位置0儲存的內容）。

for(int i = 0;i<types.length;i++){

slot += types[i].getSize();//long,double的size為2

}

/*

* 判斷原來的方法用到了哪些局部變量,獲得局部變量中已經用到的最大索引

* 將新產生的局部變量加到最大索引后,本來準備自己寫的

* BCEL中已經這樣的方法了

*/

LocalVariableGen lvg = wrapgen.addLocalVariable("starttime", Type.LONG, null, null);

//先插入一條打印語句不使用局部變量

InstructionList printlnList = ifact.createPrintln("start test start test start test start test");

InvokeInstruction invokestatic = ifact.createInvoke("java.lang.System",

"currentTimeMillis", Type.LONG, Type.NO_ARGS, Constants.INVOKESTATIC);

InstructionHandle firstHandle = printlnList.append(invokestatic);

//這個會不會將局部變量為2的地方的局部變量給覆蓋,然后此局部變量也沒有定義名字??slot這個index怎么來確定

//slot現在應該為2,之前代碼塊放的是result信息是aload,

//寫到新產生的局部變量的索引處

printlnList.append(InstructionFactory.createStore(Type.LONG, lvg.getIndex()));

//加入到之前的inlist中

ilist.insert(printlnList);

//

//在語句最后在打印結束語句,不能簡單插入在最后面,加入方法有返回值,則要插入在return 之前

//在return的時候，還要先將return的引用加入到操作數棧,怎么獲取result在局部變量中index

InstructionHandle insertposition =null;

if(returnType.getType()!=Type.VOID.getType()){

insertposition = ilist.getEnd().getPrev()；

}else{

//返回值為Type.void的話,由于沒有返回值，因此只需要在return指令前加就夠了,往前取一個即可

insertposition = ilist.getEnd();

}

InstructionList tempList = new InstructionList();

tempList.append(ifact.createFieldAccess("java.lang.System"

, "out", new ObjectType("java.io.PrintStream"),

Constants.GETSTATIC));

tempList.append(InstructionFactory.DUP);

String text = "Call to method "+wrapgen.getName()+" took ";

tempList.append(new PUSH(pgen,text));

tempList.append(ifact.createInvoke("java.io.PrintStream",

"print", Type.VOID, new Type[]{Type.STRING},

Constants.INVOKEVIRTUAL));

tempList.append(ifact.createInvoke("java.lang.System",

"currentTimeMillis", Type.LONG, Type.NO_ARGS,

Constants.INVOKESTATIC));

//獲取之前的的starttime局部變量

tempList.append(InstructionFactory.createLoad(Type.LONG, lvg.getIndex()));

tempList.append(InstructionConstants.LSUB);

tempList.append(ifact.createInvoke("java.io.PrintStream",

"print", Type.VOID, new Type[]{Type.LONG},

Constants.INVOKEVIRTUAL));

tempList.append(new PUSH(pgen," ms."));

tempList.append(ifact.createInvoke("java.io.PrintStream",

"println", Type.VOID, new Type[]{Type.STRING},

Constants.INVOKEVIRTUAL));

//在return之前的最后一句是打印end end end

.信息

tempList.append(ifact.createPrintln("end end end end end end end end end end"));

ilist.insert(insertposition,tempList);

// LocalVariableGen lvgen = new LocalVariableGen(slot,"start",Type.LONG,null,null);

//finalize the construted method

wrapgen.stripAttributes(false);

wrapgen.setMaxStack();

wrapgen.setMaxLocals();

cgen.addMethod(wrapgen.getMethod());

System.out.println();

System.out.println(wrapgen.getInstructionList());

ilist.dispose();

}

public static void main(String[] args) {

args[0]="D:\\java to eclipse\\javaeclipsestudy\\workspace\\BCELTest\\bin\\StringBuilder.class";

args[1]="buildString";

String targetClassfile = "StringBuilder.class";

if(args.length==2 && args[0].endsWith(".class")){

try{

JavaClass jclas = new ClassParser(args[0]).parse();

ClassGen cgen = new ClassGen(jclas);

Method[] methods = jclas.getMethods();

int index;

for(index =0;index<methods.length;index++){

if(methods[index].getName().equals(args[1])){

break;

}

if(index<methods.length){

modifyWrapper(cgen,methods[index]);

FileOutputStream fos = new FileOutputStream(targetClassfile);

cgen.getJavaClass().dump(fos);

fos.close();

}else{

System.err.println("Method " + args[1]+"not found in"+ args[0]);

}

}catch(Exception e){

e.printStackTrace();

}

}else{

System.out.println("usage: class-file method-name");

}

posted on 2009-08-13 22:53 Frank_Fang 閱讀(1987) 評論(2) 編輯收藏所屬分類: bcel javassist

評論:

# re: 用 BCEL 設計字節碼（二）直接在原方法上加指令 2009-08-15 20:59 | Frank_Fang

--------------------------------33
--------------------------------33
0
2
CONSTANT_Utf8[1]("SourceFile")
true
CONSTANT_Utf8[1]("StringBuilder.java")
1
StringBuilder.java
StringBuilder.java
---------------------------------------------------------------------------
1:CONSTANT_Class[7](name_index = 2)
2:CONSTANT_Utf8[1]("StringBuilder")
3:CONSTANT_Class[7](name_index = 4)
4:CONSTANT_Utf8[1]("java/lang/Object")
5:CONSTANT_Utf8[1]("")
6:CONSTANT_Utf8[1]("()V")
7:CONSTANT_Utf8[1]("Code")
8:CONSTANT_Methodref[10](class_index = 3, name_and_type_index = 9)
9:CONSTANT_NameAndType[12](name_index = 5, signature_index = 6)
10:CONSTANT_Utf8[1]("LineNumberTable")
11:CONSTANT_Utf8[1]("LocalVariableTable")
12:CONSTANT_Utf8[1]("this")
13:CONSTANT_Utf8[1]("LStringBuilder;")
14:CONSTANT_Utf8[1]("buildString")
15:CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
16:CONSTANT_String[8](string_index = 17)
17:CONSTANT_Utf8[1]("")
18:CONSTANT_Class[7](name_index = 19)
19:CONSTANT_Utf8[1]("java/lang/StringBuilder")
20:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 23)
21:CONSTANT_Class[7](name_index = 22)
22:CONSTANT_Utf8[1]("java/lang/String")
23:CONSTANT_NameAndType[12](name_index = 24, signature_index = 25)
24:CONSTANT_Utf8[1]("valueOf")
25:CONSTANT_Utf8[1]("(Ljava/lang/Object;)Ljava/lang/String;")
26:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 27)
27:CONSTANT_NameAndType[12](name_index = 5, signature_index = 28)
28:CONSTANT_Utf8[1]("(Ljava/lang/String;)V")
29:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 30)
30:CONSTANT_NameAndType[12](name_index = 31, signature_index = 32)
31:CONSTANT_Utf8[1]("append")
32:CONSTANT_Utf8[1]("(C)Ljava/lang/StringBuilder;")
33:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 34)
34:CONSTANT_NameAndType[12](name_index = 35, signature_index = 36)
35:CONSTANT_Utf8[1]("toString")
36:CONSTANT_Utf8[1]("()Ljava/lang/String;")
37:CONSTANT_Fieldref[9](class_index = 38, name_and_type_index = 40)
*********************ConstantFieldref start**********************
cc.toString : CONSTANT_Class[7](name_index = 39)
java/lang/System
cnat.toString : CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
out
Ljava/io/PrintStream;
**********************ConstantFieldref end*******************************
38:CONSTANT_Class[7](name_index = 39)
39:CONSTANT_Utf8[1]("java/lang/System")
40:CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
41:CONSTANT_Utf8[1]("out")
42:CONSTANT_Utf8[1]("Ljava/io/PrintStream;")
43:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 46)
44:CONSTANT_Class[7](name_index = 45)
45:CONSTANT_Utf8[1]("java/io/PrintStream")
46:CONSTANT_NameAndType[12](name_index = 47, signature_index = 28)
47:CONSTANT_Utf8[1]("println")
48:CONSTANT_Utf8[1]("length")
49:CONSTANT_Utf8[1]("I")
50:CONSTANT_Utf8[1]("result")
51:CONSTANT_Utf8[1]("Ljava/lang/String;")
52:CONSTANT_Utf8[1]("i")
53:CONSTANT_Utf8[1]("main")
54:CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
55:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 9)
56:CONSTANT_Methodref[10](class_index = 57, name_and_type_index = 59)
57:CONSTANT_Class[7](name_index = 58)
58:CONSTANT_Utf8[1]("java/lang/Integer")
59:CONSTANT_NameAndType[12](name_index = 60, signature_index = 61)
60:CONSTANT_Utf8[1]("parseInt")
61:CONSTANT_Utf8[1]("(Ljava/lang/String;)I")
62:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 63)
63:CONSTANT_NameAndType[12](name_index = 14, signature_index = 15)
64:CONSTANT_String[8](string_index = 65)
65:CONSTANT_Utf8[1]("Constructed string of length ")
66:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 67)
67:CONSTANT_NameAndType[12](name_index = 48, signature_index = 68)
68:CONSTANT_Utf8[1]("()I")
69:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 70)
70:CONSTANT_NameAndType[12](name_index = 31, signature_index = 71)
71:CONSTANT_Utf8[1]("(I)Ljava/lang/StringBuilder;")
72:CONSTANT_Utf8[1]("argv")
73:CONSTANT_Utf8[1]("[Ljava/lang/String;")
74:CONSTANT_Utf8[1]("inst")
75:CONSTANT_Utf8[1]("SourceFile")
76:CONSTANT_Utf8[1]("StringBuilder.java")
--------------------------域----------------------------
-----------域的長度,此類定義的成員變量的個數-------------0

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱

CONSTANT_Utf8[1]("")
方法簽名
()V
CONSTANT_Utf8[1]("()V")
方法的參數類型
方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 47
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 5
給出該方法在執行中任何點操作數棧上字的最大個數 1
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 1
code的字節信息調用code.getCode()返回byte[] [B@10b4199
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======1
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=5| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
完整的code.toString的信息
public void ()
Code(max_stack = 1, max_locals = 1, code_length = 5)
0: aload_0
1: invokespecial java.lang.Object. ()V (8)
4: return

Attribute(s) =
LineNumber(0, 2)
LocalVariable(start_pc = 0, length = 5, index = 0:StringBuilder this)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
2
方法訪問名稱
buildString
CONSTANT_Utf8[1]("buildString")
方法簽名
(I)Ljava/lang/String;
CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
方法的參數類型
int方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 143
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 51
給出該方法在執行中任何點操作數棧上字的最大個數 3
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@1ffbd68
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=48 | lv.getName()=length| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=3| lv.getLength=48| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=5| lv.getLength=37| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=3
完整的code.toString的信息
private String buildString(int length)
Code(max_stack = 3, max_locals = 4, code_length = 51)
0: ldc "" (16)
2: astore_2
3: iconst_0
4: istore_3
5: goto #37
8: new (18)
11: dup
12: aload_2
13: invokestatic java.lang.String.valueOf (Ljava/lang/Object;)Ljava/lang/String; (20)
16: invokespecial java.lang.StringBuilder. (Ljava/lang/String;)V (26)
19: iload_3
20: bipush 26
22: irem
23: bipush 97
25: iadd
26: i2c
27: invokevirtual java.lang.StringBuilder.append (C)Ljava/lang/StringBuilder; (29)
30: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
33: astore_2
34: iinc %3 1
37: iload_3
38: iload_1
39: if_icmplt #8
42: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
45: aload_2
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: aload_2
50: areturn

Attribute(s) =
LineNumber(0, 6), LineNumber(3, 7), LineNumber(8, 8), LineNumber(34, 7),
LineNumber(42, 10), LineNumber(49, 12)
LocalVariable(start_pc = 0, length = 51, index = 0:StringBuilder this)
LocalVariable(start_pc = 0, length = 51, index = 1:int length)
LocalVariable(start_pc = 3, length = 48, index = 2:String result)
LocalVariable(start_pc = 5, length = 37, index = 3:int i)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
9
方法訪問名稱
main
CONSTANT_Utf8[1]("main")
方法簽名
([Ljava/lang/String;)V
CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
方法的參數類型
java.lang.String[]方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 159
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 59
給出該方法在執行中任何點操作數棧上字的最大個數 4
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@ec16a4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=59| lv.getNameIndex()=72 | lv.getName()=argv| lv.getSignatureIndex()=73 | lv.getSignature()=[Ljava/lang/String; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=8| lv.getLength=51| lv.getNameIndex()=74 | lv.getName()=inst| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=10| lv.getLength=48| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=24| lv.getLength=25| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=3
完整的code.toString的信息
public static void main(String[] argv)
Code(max_stack = 4, max_locals = 4, code_length = 59)
0: new (1)
3: dup
4: invokespecial StringBuilder. ()V (55)
7: astore_1
8: iconst_0
9: istore_2
10: goto #52
13: aload_1
14: aload_0
15: iload_2
16: aaload
17: invokestatic java.lang.Integer.parseInt (Ljava/lang/String;)I (56)
20: invokespecial StringBuilder.buildString (I)Ljava/lang/String; (62)
23: astore_3
24: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
27: new (18)
30: dup
31: ldc "Constructed string of length " (64)
33: invokespecial java.lang.StringBuilder. (Ljava/lang/String;)V (26)
36: aload_3
37: invokevirtual java.lang.String.length ()I (66)
40: invokevirtual java.lang.StringBuilder.append (I)Ljava/lang/StringBuilder; (69)
43: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: iinc %2 1
52: iload_2
53: aload_0
54: arraylength
55: if_icmplt #13
58: return

Attribute(s) =
LineNumber(0, 17), LineNumber(8, 18), LineNumber(13, 19), LineNumber(24, 20),
LineNumber(36, 21), LineNumber(46, 20), LineNumber(49, 18), LineNumber(58, 23)

LocalVariable(start_pc = 0, length = 59, index = 0:String[] argv)
LocalVariable(start_pc = 8, length = 51, index = 1:StringBuilder inst)
LocalVariable(start_pc = 10, length = 48, index = 2:int i)
LocalVariable(start_pc = 24, length = 25, index = 3:String result)

end method method method-----------------------------------

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# re: 用 BCEL 設計字節碼（二）直接在原方法上加指令 2009-08-15 21:08 | Frank_Fang

這個是修改后的方法的字節碼信息

--------------------------------33
--------------------------------33
0
2
CONSTANT_Utf8[1]("SourceFile")
true
CONSTANT_Utf8[1]("StringBuilder.java")
1
StringBuilder.java
StringBuilder.java
---------------------------------------------------------------------------
1:CONSTANT_Class[7](name_index = 2)
2:CONSTANT_Utf8[1]("StringBuilder")
3:CONSTANT_Class[7](name_index = 4)
4:CONSTANT_Utf8[1]("java/lang/Object")
5:CONSTANT_Utf8[1]("<init>")
6:CONSTANT_Utf8[1]("()V")
7:CONSTANT_Utf8[1]("Code")
8:CONSTANT_Methodref[10](class_index = 3, name_and_type_index = 9)
9:CONSTANT_NameAndType[12](name_index = 5, signature_index = 6)
10:CONSTANT_Utf8[1]("LineNumberTable")
11:CONSTANT_Utf8[1]("LocalVariableTable")
12:CONSTANT_Utf8[1]("this")
13:CONSTANT_Utf8[1]("LStringBuilder;")
14:CONSTANT_Utf8[1]("buildString")
15:CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
16:CONSTANT_String[8](string_index = 17)
17:CONSTANT_Utf8[1]("")
18:CONSTANT_Class[7](name_index = 19)
19:CONSTANT_Utf8[1]("java/lang/StringBuilder")
20:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 23)
21:CONSTANT_Class[7](name_index = 22)
22:CONSTANT_Utf8[1]("java/lang/String")
23:CONSTANT_NameAndType[12](name_index = 24, signature_index = 25)
24:CONSTANT_Utf8[1]("valueOf")
25:CONSTANT_Utf8[1]("(Ljava/lang/Object;)Ljava/lang/String;")
26:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 27)
27:CONSTANT_NameAndType[12](name_index = 5, signature_index = 28)
28:CONSTANT_Utf8[1]("(Ljava/lang/String;)V")
29:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 30)
30:CONSTANT_NameAndType[12](name_index = 31, signature_index = 32)
31:CONSTANT_Utf8[1]("append")
32:CONSTANT_Utf8[1]("(C)Ljava/lang/StringBuilder;")
33:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 34)
34:CONSTANT_NameAndType[12](name_index = 35, signature_index = 36)
35:CONSTANT_Utf8[1]("toString")
36:CONSTANT_Utf8[1]("()Ljava/lang/String;")
37:CONSTANT_Fieldref[9](class_index = 38, name_and_type_index = 40)
*********************ConstantFieldref start**********************
cc.toString : CONSTANT_Class[7](name_index = 39)
java/lang/System
cnat.toString : CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
out
Ljava/io/PrintStream;
**********************ConstantFieldref end*******************************
38:CONSTANT_Class[7](name_index = 39)
39:CONSTANT_Utf8[1]("java/lang/System")
40:CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
41:CONSTANT_Utf8[1]("out")
42:CONSTANT_Utf8[1]("Ljava/io/PrintStream;")
43:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 46)
44:CONSTANT_Class[7](name_index = 45)
45:CONSTANT_Utf8[1]("java/io/PrintStream")
46:CONSTANT_NameAndType[12](name_index = 47, signature_index = 28)
47:CONSTANT_Utf8[1]("println")
48:CONSTANT_Utf8[1]("length")
49:CONSTANT_Utf8[1]("I")
50:CONSTANT_Utf8[1]("result")
51:CONSTANT_Utf8[1]("Ljava/lang/String;")
52:CONSTANT_Utf8[1]("i")
53:CONSTANT_Utf8[1]("main")
54:CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
55:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 9)
56:CONSTANT_Methodref[10](class_index = 57, name_and_type_index = 59)
57:CONSTANT_Class[7](name_index = 58)
58:CONSTANT_Utf8[1]("java/lang/Integer")
59:CONSTANT_NameAndType[12](name_index = 60, signature_index = 61)
60:CONSTANT_Utf8[1]("parseInt")
61:CONSTANT_Utf8[1]("(Ljava/lang/String;)I")
62:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 63)
63:CONSTANT_NameAndType[12](name_index = 14, signature_index = 15)
64:CONSTANT_String[8](string_index = 65)
65:CONSTANT_Utf8[1]("Constructed string of length ")
66:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 67)
67:CONSTANT_NameAndType[12](name_index = 48, signature_index = 68)
68:CONSTANT_Utf8[1]("()I")
69:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 70)
70:CONSTANT_NameAndType[12](name_index = 31, signature_index = 71)
71:CONSTANT_Utf8[1]("(I)Ljava/lang/StringBuilder;")
72:CONSTANT_Utf8[1]("argv")
73:CONSTANT_Utf8[1]("[Ljava/lang/String;")
74:CONSTANT_Utf8[1]("inst")
75:CONSTANT_Utf8[1]("SourceFile")
76:CONSTANT_Utf8[1]("StringBuilder.java")
77:CONSTANT_Utf8[1]("start test start test start test start test")
78:CONSTANT_String[8](string_index = 77)
79:CONSTANT_Utf8[1]("currentTimeMillis")
80:CONSTANT_Utf8[1]("()J")
81:CONSTANT_NameAndType[12](name_index = 79, signature_index = 80)
82:CONSTANT_Methodref[10](class_index = 38, name_and_type_index = 81)
83:CONSTANT_Utf8[1]("Call to method buildString took ")
84:CONSTANT_String[8](string_index = 83)
85:CONSTANT_Utf8[1]("print")
86:CONSTANT_NameAndType[12](name_index = 85, signature_index = 28)
87:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 86)
88:CONSTANT_Utf8[1]("(J)V")
89:CONSTANT_NameAndType[12](name_index = 85, signature_index = 88)
90:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 89)
91:CONSTANT_Utf8[1](" ms.")
92:CONSTANT_String[8](string_index = 91)
93:CONSTANT_Utf8[1]("end end end end end end end end end end")
94:CONSTANT_String[8](string_index = 93)
95:CONSTANT_Utf8[1]("starttime")
96:CONSTANT_Utf8[1]("J")
--------------------------域----------------------------
-----------域的長度,此類定義的成員變量的個數-------------0

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱
<init>
CONSTANT_Utf8[1]("<init>")
方法簽名
()V
CONSTANT_Utf8[1]("()V")
方法的參數類型
方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 47
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 5
給出該方法在執行中任何點操作數棧上字的最大個數 1
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 1
code的字節信息調用code.getCode()返回byte[] [B@1ffb8dc
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======1
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=5| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
完整的code.toString的信息
public void <init>()
Code(max_stack = 1, max_locals = 1, code_length = 5)
0: aload_0
1: invokespecial java.lang.Object.<init> ()V (8)
4: return

Attribute(s) =
LineNumber(0, 2)
LocalVariable(start_pc = 0, length = 5, index = 0:StringBuilder this)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
9
方法訪問名稱
main
CONSTANT_Utf8[1]("main")
方法簽名
([Ljava/lang/String;)V
CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
方法的參數類型
java.lang.String[]方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 159
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 59
給出該方法在執行中任何點操作數棧上字的最大個數 4
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@ec16a4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=59| lv.getNameIndex()=72 | lv.getName()=argv| lv.getSignatureIndex()=73 | lv.getSignature()=[Ljava/lang/String; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=8| lv.getLength=51| lv.getNameIndex()=74 | lv.getName()=inst| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=10| lv.getLength=48| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=24| lv.getLength=25| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=3
完整的code.toString的信息
public static void main(String[] argv)
Code(max_stack = 4, max_locals = 4, code_length = 59)
0: new <StringBuilder> (1)
3: dup
4: invokespecial StringBuilder.<init> ()V (55)
7: astore_1
8: iconst_0
9: istore_2
10: goto #52
13: aload_1
14: aload_0
15: iload_2
16: aaload
17: invokestatic java.lang.Integer.parseInt (Ljava/lang/String;)I (56)
20: invokespecial StringBuilder.buildString (I)Ljava/lang/String; (62)
23: astore_3
24: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
27: new <java.lang.StringBuilder> (18)
30: dup
31: ldc "Constructed string of length " (64)
33: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
36: aload_3
37: invokevirtual java.lang.String.length ()I (66)
40: invokevirtual java.lang.StringBuilder.append (I)Ljava/lang/StringBuilder; (69)
43: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: iinc %2 1
52: iload_2
53: aload_0
54: arraylength
55: if_icmplt #13
58: return

Attribute(s) =
LineNumber(0, 17), LineNumber(8, 18), LineNumber(13, 19), LineNumber(24, 20),
LineNumber(36, 21), LineNumber(46, 20), LineNumber(49, 18), LineNumber(58, 23)

LocalVariable(start_pc = 0, length = 59, index = 0:String[] argv)
LocalVariable(start_pc = 8, length = 51, index = 1:StringBuilder inst)
LocalVariable(start_pc = 10, length = 48, index = 2:int i)
LocalVariable(start_pc = 24, length = 25, index = 3:String result)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
2
方法訪問名稱
buildString
CONSTANT_Utf8[1]("buildString")
方法簽名
(I)Ljava/lang/String;
CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
方法的參數類型
int方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 198
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 96
給出該方法在執行中任何點操作數棧上字的最大個數 6
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 6
code的字節信息調用code.getCode()返回byte[] [B@1c29ab2
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======5
--------------------第 0 個局部變量的信息
lv.getStartPC()=13| lv.getLength=83| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=13| lv.getLength=83| lv.getNameIndex()=48 | lv.getName()=length| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=16| lv.getLength=80| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=18| lv.getLength=40| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=3
--------------------第 4 個局部變量的信息
lv.getStartPC()=0| lv.getLength=96| lv.getNameIndex()=95 | lv.getName()=starttime| lv.getSignatureIndex()=96 | lv.getSignature()=J |lv.getIndex()=4
完整的code.toString的信息
private String buildString(int length)
Code(max_stack = 6, max_locals = 6, code_length = 96)
0: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
3: ldc "start test start test start test start test" (78)
5: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
8: invokestatic java.lang.System.currentTimeMillis ()J (82)
11: lstore %4
13: ldc "" (16)
15: astore_2
16: iconst_0
17: istore_3
18: goto #50
21: new <java.lang.StringBuilder> (18)
24: dup
25: aload_2
26: invokestatic java.lang.String.valueOf (Ljava/lang/Object;)Ljava/lang/String; (20)
29: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
32: iload_3
33: bipush 26
35: irem
36: bipush 97
38: iadd
39: i2c
40: invokevirtual java.lang.StringBuilder.append (C)Ljava/lang/StringBuilder; (29)
43: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
46: astore_2
47: iinc %3 1
50: iload_3
51: iload_1
52: if_icmplt #21
55: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
58: aload_2
59: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
62: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
65: dup
66: dup
67: ldc "Call to method buildString took " (84)
69: invokevirtual java.io.PrintStream.print (Ljava/lang/String;)V (87)
72: invokestatic java.lang.System.currentTimeMillis ()J (82)
75: lload %4
77: lsub
78: invokevirtual java.io.PrintStream.print (J)V (90)
81: ldc " ms." (92)
83: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
86: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
89: ldc "end end end end end end end end end end" (94)
91: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
94: aload_2
95: areturn

Attribute(s) =
LocalVariable(start_pc = 13, length = 83, index = 0:StringBuilder this)
LocalVariable(start_pc = 13, length = 83, index = 1:int length)
LocalVariable(start_pc = 16, length = 80, index = 2:String result)
LocalVariable(start_pc = 18, length = 40, index = 3:int i)
LocalVariable(start_pc = 0, length = 96, index = 4:long starttime)
LineNumber(13, 6), LineNumber(16, 7), LineNumber(21, 8), LineNumber(47, 7),
LineNumber(55, 10), LineNumber(94, 12)

end method method method-----------------------------------

可以看出局部變量this 的start_pc顯然是不正確的
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